INSULATING VACUUM JACKET SUITABLE FOR THERMAL VESSELS CONTAINING LIQUIDS AND IN PARTICULAR AQUEOUS AND/OR ORGANIC LIQUIDS

Abstract: An insulating jacket (5) under vacuum, suitable for thermal vessels containing liquids, and in particular aqueous and/or organic liquids, containing, as a material (7) sorbing the residual gases present in said jacket after the evacuation, prevailingly consisting of hydrogen, carbon monoxide, carbon dioxide and water, a combination of barium oxide (BaO) with palladium oxide (PdO) and/or with another oxide of a noble metal selected from ruthenium, rhodium, osmium, iridium and silver.

Description: "INSULATING VACUUM JACKET SUITABLE FOR THERMAL VESSELS CONTAINING LIQUIDS AND IN PARTICULAR AQUEOUS AND/OR ORGANIC LIQUIDS" The invention relates to an insulating vacuum jacket suitable for thermal vessels containing liquids and in particular aqueous and/or organic liquids like coffe, tea, warm milk, broth, juices, alcoholics and beverages like wine or beer, refreshments or chilled soft drinks and other beverages needing to be kept a long time at a temperature higher or lower than room tempe¬ rature. Other examples of a liquid of this kind may be the solutions or the suspensions (for instance of aqueous or hydroalcoholic nature) of pharmaceutical and/or biological products, of samples of antifreeze products, of particular compounds of radioisotopes and so on. As a matter of principle, the jacket accord¬ ing to the invention can be used also for DEWAR vessels and for other cyogenic devices (for instance insulated pipings), provided there is no presence of liquid hydrogen. British patent 921,273 teaches to insulate vessels containing non-aqueous liquids, for instance liquid oxygen or nitrogen, by means of a vacuum jacket, made from glass or metal, containing a combination of palladium oxide (PdO) with a material selected from zeolites, charcoal and silica gel, showing sorption activity with respect to hydrogen. The purpose of said combination was to maintain a long time the desired vacuum level in the insulating jacket, by sorption of the residual gases, already present in the jacket since the beginning (or generat¬ ed in a subsequent time) by degassing of the jacket's 5 walls or consequently to leaks through the same walls. Said residual gases are mainly hydrogen, carbon monoxi¬ de, carbon dioxide and water. Zeolites however have a limited sorption capa¬ city with respect to carbon dioxide (and a practically 10 null capacity with respect to carbon monoxide and hydrogen) and if the temperature of the aqueous liquid (for instance coffee) is higher than the outer tempe¬ rature, also the sorption capacity with respect to water is poor; furthermore, the activation of zeolites ■ t - requires a prolonged heat treatment, thus rendering their exploitation very far from cheap, especially on occasion of a mass-use. That is why, until now, no vacuum bottle (thermos) was ever employed for the aqueous liquids when containing said combinations. 0 The replacement of zeolites by charcoal and/or silica gel does not involve any appreciable improve¬ ment . Italian patent 1,191,11^, granted to the Appli¬ cant, suggested to replace said combinations, based 5 on palladium oxide, by particular alloys based on zirconium, allowing a slight improvement just in the presence of aqueous liquids in a vacuum bottle. Even such alloys, however, do not have a high sorption capacity with respect to water vapour and to the other Q residual gases, requiring moreover a high activation temperature (573 K or even more). Furthermore, in such cases, in order to minimize the gas load, the thermos has to undergo, during the manufacturing step, a prolonged heat treatment under pumping. The drawbacks hereinabove have now overcome by the Applicant, which discovered a pretty good combi¬ nation based on palladium oxide, to be inserted into the insulating jackets of the vacuum bottles. In its broadest aspect, the invention relates to an insulating vacuum jacket, suitable for thermal vessels containing aqueous and/or organic liquids, and in particular for the so-called thermos, containing as the sorption material for the residual gases present in the jacket, essentially consisting or hydrogen, carbon monoxide, carbon dioxide and water, a combina¬ tion of palladium oxide (PdO) and barium oxide (BaO). Palladium oxide can be optionally replaced, in a part¬ ial or complete way, by ruthenium oxide, rhodium oxide, osmium oxide, iridium oxide or silver oxide. Palladium oxide (or the other oxides of noble metals) can be used as such or in a supported form; the carrier may be consisting for instance of alumina, silica, silicalites or titanium-silicalites , having a 2 surface area from 10 to 600 m /g (pore diameter = from 0,5 to 100 nanometer) and the combination to be placed in the jacket may be in the form of a powder or in the form of pellets, granules, rings, Berl sadd¬ les and so on. According to a particular embodiment, there is first prepared an aqueous solution of a water-solu¬ ble palladium salt, for instance chloride or nitrate, - k - and then the carrier, for instance alumina, may be impregnated by means of a predetermined technique, e.g. by the soaking technology or by the so-called dry impregnation, namely a technology according to which the volume of the impregnating solution is equal to or lower than the overall volume of the carrier's pores. A precipitation is then achieved by means of an alkaline solution (preferably from pH 7 to pH 12) and the reaction mixture is filtered and brought to dryness at a temperature lower than 500°C. The thus obtained powder ( ranulometry = from 0.5 to 200 micro¬ meter) is then admixed with barium oxide in the form of a powder (granulometry = from 0.5 to 500 micrometer) and optionally with traces of binders and/or lubricat- ing agents; then the mixture is compressed into pellets which are loaded into the thermally insulating jackets- to be evacuated. The attached drawings are supplied for merely illustrative purposes and do not limit in any case the scope and the spirit of the invention: FIGURE 1 is the cross-section of a thermos having an insulating jacket according to the present inventio ; FIGURE 2 is the layout of a method for evacuat- i n g said jacket; FIGURES 3, k and 5 do report a few of the results ensuing the tests of the examples. Following Fig. 1, a thermos 1 is consisting of an inner cylindrical vessel 2, made from metal or glass, defining an inner volume or useful space 3, suitable for containing aqueous liquids and in particu- lar hot or chilled beverages, in communication with the outside by means of a neck 6, normally closed but not sealed. An external wall or mantel (shell) defines, together with the wall of the vessel 2, a jacket (inter- space) 5 under vacuum; this jacket during the evacuat¬ ion, in the manufacturing phase of the thermos, is in communication with a vacuum pump not recorded on the drawing. The interspace pressure, once the pumping is -3 over, is normally equal to or lower than 5 x 10 -4 -6 mbar and preferably from 10 to 10 bar, when no insulating material is present. Should the interspace contain insulating material, the maximum allowable pressure may be higher, for instance a pressure up to 0.1 mbar. The combination of (optionally supported) PdO and of BaO (7)-. according to a weight ratio PdO/BaO approximately comprised between 1 : 1 and 1 : 1000 (preferably from 1 : 2 to 1: 200) is arranged in contact with the mantel 4. Optionally the new combinations (e.g. BaO ÷ PdO) may be contained in a thermoretract- able housing, of the type described in US patent 5, 191,980. The following examples are supplied for merely illustrative purposes and do not limit in any case and in any way the scope and the spirit of the invention. Example 1 (conditions common to examples 2 and 3) An apparatus suitable for measuring the gas- sorption properties of the sorbing materials according to the present invention is recorded on Fig. 2. Such figure shows, in a schematical way. a device 100 measuring the sorption features of mixtures of BaO and PdO as well as of other comparison mixtures. A vacuum pumping system 102 is connected to a metering volume 106 by means of a first valve 104. A series of second valves 110, 110' , 110" is connected to said metering volume, in order to allow the inlet of test gases, coming from a series of test flasks 112, 112' , 112" respectively containing H , CO and CO, as well as a pressure gauge 114. A test flask 118, containing the specimen 120 to be tested is connect- ed to the metering volume lθ6 by means of a third valve ll6. During the test run, valves 110, 110' , 110" and ll6 are closed and valve 114 was open, whereas the vacuum pumping system 102 decreased the system -6 pressure down to 10 mbar. Metering volume 106 had a capacity of about. 0.8 liter for each performed test. Apparatus 100 was connected, through (closed) valve 116, to a specimen 120 contained in a test gas flask llδ having approxima- tely a volume of 0.3 liter, under an inert argon atmo¬ sphere . During the tests valve 116 was opened and -6 the system was once more evacuated, down to 10 mbar, while the specimen was kept about 100°C for 15 minutes, which was simulating a cycle similar to the ones which can be encountered by the adsorbing combination, and then the specimen was allowed to cool to room tempera¬ ture. Valves 104 and 116 were then closed and the test gas, coming from the gas flask 112. (112' , 112"), was allowed τo flow into the metering volume 106 for a short period of time. Pressure was recorded on gauce ll4 and controlled as to be approximately between 0.2 and 0.5 mbar, after opening valve ll6. bringing a metered amount of test gas into contact with specimen 120. Example 2 One gram of barium oxide, in the form of a powder and having a granulometry lower than 125 micro¬ meter, was admixed with 2 g of granules (average size lower than 600 micrometer) of palladium oxide support- ed by porous alumina, the PdO title being 2% b.w. The specimen was then connected to the test¬ ing apparatus of Example 1. Then a first metered amount of gas, in this case carbon monoxide (from flask 112, by means of valve 110) was brought into contact with the specimen. Pressure, in the vessel, was measured as a function of time by means of instrumentation 114; the resulting plot was recorded on Fig. 3 as line 1. Successively, other metered amounts of other gases (H , CO and so on) were allowed to sequentially c * __ flow through the specimen, following the same procedur¬ al pattern. The corresponding lines, showing the pressure trend along with the time, are respectively recorded on Fig. 3 as lines 2 and ~ . In each case the specimen did show higher sorption features, either in terms of sorption velocity or in terms of sorption capacity, with respect to the sorption materials of the prior art. Example 3 (comparative) This example shows the behaviour of a conven¬ tional material, like the ones generally exploited for the realization of an evacuated interspace in 5 view of a thermal insulation. One gram of synthetic zeolites, of the 13X class (pore diameter = 1 nanometer), in the form of (cylindrical) pellets having a 1/8" diameter (3.2 mm) supplied by Davidson Chemicals Co., were admixed with 10 4θ mg of palladium oxide, in the form of a powder, having a granulometry lower than 125 micrometer. The specimen (llδ) was then connected to the testing apparatus of Example 1. The procedure of Exam¬ ple 2 was then followed, by exposing the specimen to 15 successive metered amounts of gas, in the order hydro¬ gen, carbon monoxide and carbon dioxide. The correspond¬ ing lines, showing the pressure trend along the time, are respectively recorded, on Fig. 4, as lines 1, 2 and 3. 20 The results of such tests point out sorption features which can be measured only in the case of hydrogen and CO . In the case of carbon monoxide (line l) no pressure reduction was registered from a practical point of view. 25 Example 4 Approximately 500 mg of barium oxide, in the form of a powder showing a granulometry lower than 125 micrometer, were admixed with 250 mg of granules (average size lower than 600 micrometer) consisting • j o °f palladium oxide, supported on porous alumina, and having a PdO content equal to 2% b.w. The mixture was then loaded into a system like the one described by ASTM-F-798-82 , concerning the standards allowing to determine the gettering degree, the sorption capacity and the gas concentration in non-evaporable getters (NEG) in the field of the molecular flow. After having submitted the system to degassing under pumping, at about 150°C for 7 h, and after having allowed the specimen to cool to room temperature (ca. 25°C), the sorption tests were started by admitting first hydrogen to the specimen and subsequently carbon monoxide. Both the tests were carried out by maintain¬ ing a constant pressure on the specimen, equal to 4 x mbar. The thus obtained sorption lines are record- ed on Fig. 5

Claims: CLAIMS 1. An insulating jacket under vacuum, suitable for thermal vessels containing liquids, and in parti¬ cular aqueous and/or organic liquids, containing, as a material sorbing the residual gases present in said jacket, prevailingly consisting of hydrogen, carbon monoxide, carbon dioxide and water, a combination of barium oxide (BaO) with palladium oxide (PdO) and/or with another oxide of a noble metal selected from ruthenium, rhodium, osmium, iridium and silver. 2. A jacket according to claim 1, wherein said oxide of palladium or of other noble metal is in a supported form. ~ . A jacket according to claim 1, wherein said noble metal oxide, different from palladium oxide, is ruthenium oxide. 4. The jacket of claim 2, wherein the carrier is selected from alumina, silica, silicalites and titanium-silicalites , and wherein the surface area of 2 the carrier is from 10 to 600 m /g (pore diameter from 1 to 100 nanometer). 5. The jacket of claim 2, wherein said combina¬ tion is present in the form of a powder. 6. The jacket of claim 2, wherein said combina¬ tion is present in a form selected from pellets, granu- les , rings and Berl saddles. 7- The jacket of claim 2, wherein said support¬ ed palladium oxide is present in a form obtained from the aqueous solution of α water soluble palladium salt, in particular chloride or nitrate, by precipita- tion by means of an alkaline solution in the presence of the carrier. 8. A method for the preparation of the combina¬ tion according to claim 7- wherein said carrier, in the form of a powder, is first impregnated by the aqueous solution of a palladium salt, according to the dry impregnation technique, wherein the thus impre¬ gnated powder is treated by means of an alkaline solut¬ ion, and wherein the resulting product is filtered, dried, converted into a powder and finally admixed with a BaO powder, the ensuing mixture being then compressed into pellets or granules. 9. The method of claim 8, wherein said carrier is alumina and wherein the weight ration PdO : BaO is from 1 : 1 and 1 : 200. 10. A thermal vessel suitable for containing liquids, thermally insulated by means of the jacket of claim 2.

Inventors: BOFFITO CLAUDIO, FERRARIO BRUNO, BOFFITO, CLAUDIO, FERRARIO, BRUNO
Applicants: GETTERS SPA, SAES GETTERS S.P.A.
Application year: 1994
Main classification: A47J41
IPC codes: A47J41, B01J20, F17C3, H01J7